<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>三栏布局</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        html,body{
            height: 100%;
        }
        .start,.footer{
            width: auto;
            /* margin-left: 400px; 
            width:100%不叫自适应，增加left会增加滚动条--即超出屏幕范围*/
            height: 100px;
            background: rgb(120, 119, 119);
        }
        .middle{
            height: calc(100% - 200px);
            background: #000;
        }
        .left,.right{
            width: 100px;
            height: 150px;
            float: left;
            background: rgb(196, 192, 159);
        }
        .center{
            width: calc(100% - 200px);
            height: 100%;
            float: left;
            background: rgb(54, 58, 53);
        }
    </style>
</head>
<body>
    <div class="start"></div>
    <div class="middle">
        <div class="left"></div>
        <div class="center"></div>
        <div class="right"></div>
    </div>
    <div class="footer"></div>
</body>
</html>